Making Sense of Many Lipids

Homeostatic mechanisms maintain the lipid composition of biological membranes. In mammalian cells, the sterol regulatory element-binding proteins are transcription factors that regulate cellular levels of cholesterol and fatty acids in a signaling and feedback mechanism that responds to these very lipids. Dobrosotskaya et al. (see the Perspective by Nohturfft and Losick) report that this pathway is conserved in flies but also responds to and regulates synthesis of cellular phospholipids, a major membrane lipid.